Note: Australia is generally considered to be a continental landmass, rather than an island. If however one does count Australia among the islands it, not Greenland, would be the largest in the world (unless one also considered Antarctica an island).
... Lake Indian Reservation[?]
Standing Rock Indian Reservation[?]
Cheyenne River Sioux Indian Reservation[?]
Lake Traverse Indian Reservation[?]
Lower Brule Indian ...